aniel_

I've been using 5w-30 castrol GTX, in my 1989 rx-7 gtu, for at least two years know, through the extreme temperature variations of the midwest, my car runs excellent at the moment, should i continue using 5w-30 or switch to 10w-30?

chris_stampe

If it works then leave it, thats what I use and it gets pretty cold in our region so Id say its better to have too light of weight that to heavy imo.
Chris

Samps

You should be fine for the summer months but I would not recommend using that in the colder months. Try 20w-50 in the winter. But GTX is my weapon of choice, per recommendation of Dave at KDR.

darkwaveboi

if its been doing what you need, keep it like chris said.

wozzoom

You've got it backwards. Use 20W-50 in the summer, 10W-30 in the winter.

Doesn't anyone read the owners manual? 10W-30 is for use when outside temps are below 90 degrees. 20W-50 covers you up to somthing like 120 degrees if I recall correctly.

Check the manual!

Supermac 7

Wozzoom is correct. I use 20W-50 year round, but in my old N/A, I used 10W-30 in the winter so the car would warm up a little quicker because of the lighter weight nature of the oil.

Samps

Thanks for correcting my mistake.

silverrotor

iTrader: (1)

Hey Samps, It's all good. But just to beat a dead horse , using 20w-50 In the winter months would be a killer for any car to warm up. The oil would be as thick as mollasess.

Turbonut

iTrader: (1)

As stated earlier..Check the manual!!!

Samps

Yep! I was typing faster than I was thinking. I don't have much time to browse the forum anymore so when I do I try to get as many responses as possible. But maybe I should concentrate more on giving 5 right answers than 8 right and 2 wrong.

Icemark

Actually 20W50 will give your engine more protection when used from 20F up than most other oil weights.

Of course if I lived in the great white north like you silverrotor, where it is way below 20F in the winter, I too might use a different (read thinner) oil in the dead of winter.

And back up to the original question about 5W30... 5W30 should not be used in temps above 30F or engine damage will occur.

RrtyRckt

I heard something about 10w-30 having to much viscosity build up. Sound familiar?

hawaiiangoat

I use 20W50 in summer, and don't drive it in winter.

deadRX7Conv

5w30 won't cause engine damage as long as you have good oil pressure from idle to redline. Oils made today are different than oils made 15+ years ago(when owners' manuals were printed). It is more important to perform frequent oil changes to prevent oil degradation and breakdown. All oils have viscosity buildup over time. Its not just an issue with one weight.

But, as a general rule, as engines wear and clearances increase, it is usually better to run a higher weight oil to maintain consistent pressure/protection.....especially in the summer. My car runs perfect on 10/30 or 10/40 year round. I also get quick oil pressure during cold starts in the winter due to a quality oil filter that doesn't empty out when shutting off car.

I don't see the need for 20w50 for any NA rotary regardless of who recommends it. At what point does oil volume decreasing or increasing better or worse than oil pressure increasing or decrease?

Thick oil is best used in completely worn engines that have too much oil pressure loss through the bearings. Rotary bearings usually last longer than the rest of the engine.

And yes wozzoom, everyone should check the owners manual. My '91 doesn't list anything other than 5/30 or 10/30. I guess that I sinned by using the 10/40.

TRURX7

15-40 in summer for me 5-30 in winter

Icemark

I think you are missing the way oils work, in that a thinner oil, when warm will have a much thinner shear wall, to prevent metal to metal contact.

That is simply how oils work, that is why there are different weights. Oil pressure is ill regardless if it is within factory specs, but the amount of oil left on the surface on any given cycle is too thin when using to light weight of oil in too warm conditions.

But hey, 10W30 is fine if you are seeing temps below 80F. But above 80F, no matter what quality oil used, the shear level is too thin at that weight.

Your motor may not blow up this week, but its life will be reduced.

deadRX7Conv

No, I didn't miss the point. To prevent metal to metal contact, you need oil pressure. Oil viscosity is irrelevent without oil pressure.

Most oils, regardless of bottle label, have almost the same viscosity when at normal operating temp. The only difference is when cold or extremely hot. No one can produce 'oil temp to oil viscosity' curves. This is something the oil companies don't want us to see. They usually rate or publish a single viscosity at sustained temp. Then, they go get the oil certified for the multiweight label. The weight of an oil is a relatively short term and simple test. Even someone mixing paint with thinner has more accuracy when counting the drips per minute and comparing it to a provided paint viscosity chart.
Because of the excellent oil cooler in the RX7, rarely does the oil temp exceed safe temperatures. If it did, then you already have other problems and the oil choice isn't gonna make a difference.
New oils are more stable than ever before. They don't break down or quit as quickly as oils from just 10 years ago.
The biggest problem with any oil is the overuse of it. 3000 mile or more oil change interval may be good in a piston engine. But, the hotter, oil cooled, oil injected, higher rpm rotary needs clean oil that hasn't started to break down.

And, if you have money to waste, feel free to send an oil sample to any one of the oil analyzers out there. You can send a fresh sample and compare it the same oil in 1000 mile increments.
If you want to look a collection of oil results, visit the maxima.org forum and download their oil analysis. You will notice that USED oil from 0w30 to 15w40 has roughly the same viscosity at 212F. Only when it is fresh from the bottle is the viscosity marginally different.
From Amsoils website:
ASTM 4ball wear test-------bull$**** grease test that amsoil uses to make their oil look the best, but good to compare the thick vs. thin argument.
The thinner oils were run at 40kg pressure at 150degrees C for an hour with so called test speed of 1800rpm.
The thicker oils were run at 60kg pressure with other test specs the same as thin oil.
Amsoil2000 0w30 .373
Amsoil2000 20w50 .440
Pennzoil 5w30 .540
Castrol syntec 5w50 .576
Mobil1 Tri 5w30 .589
QuakerState4x4 blend 10w30 .595
Mobil1 Tri 0w30 .607
Havoline Form3 20w50 .713
Valvoline synth 20w50 .741
Castrol Syntec 20w50 .757
QuakerS synth blend 20w50 .790
Mobil1 Tri 15w50 .922
The smaller the scar/scratch the better. Thick oils don't perform.
This prove that some 5w30 non synths like Pennzoil perform better than thicker oils. This blows the shear/stress argument out of the water.

Oils are like making Jello. Too much powder and it is gummy. Too like powder and it is runny. Oils use VI improvers to play with thicknesses. These don't not benefit you engine. All they do is let the bottle label change from low numbers to high numbers. The best oils use as little viscosity index improvers as possible because they are formulated well from the beginning. Cheap oils need more. So do oils with wide number spreads. 5w50 5w40 10w40 20w50 have excessive additives to maintain their wide multiweight spread. The oils with the least/narrow temp spread are the best----5w30 10w30 and 15w40 for example.

Icemark

Your additive info is off a little, actually 20W50 oils have less additive packages than 5W30, because of the higher base stock used.

You may wish to read the link on oils tests and viscosity and additives that I have posted at least 20 times on this board in that respect.

Redlines shear tests are also intresting but, because the heavier weight oils were delivered at high pressures, don't you think it invalidates the test comparing a 5W30 or 10W30 to a 20W50. It would be more inline to comparing a cheap 20W50 to the better redline 20W50

deadRX7Conv

What 20w50 have less additives packages than 5w30?
What oils use what base stock? They don't tell us that on the bottle. And, feel free to define base stock or even group type which some companies like to use to make their oil seem better than others.
What websites show additive package ratios compared to oil weights?

Sure it invalidates the test. At a lower pressure logically, the thicker oil would have caused more wear.
Would you think that higher oil pressure would prevent wear? I guess that high PSI oil regulators are milking us for more money.
If anything, the Amsoil proves that the thinner oil work better because they can protect at lower pressures at such a high temp. 150C=~300F.
Wheres the thicker oil is better at higher temps proof?

I don't care for amsoil but I was making a point.
They proved that thinner oils protect as good as thicker oils. Maybe 20 years ago the results would be different.
We spend too much time believing hearsay, old wives tales, and what great granpa told us. And there are new cars that run 5w20 year round. Not that I would do that, but there isn't a sudden collection of dead engines in new cars every summer.

You said that 20w50 will give more protection. Prove it.
You said that 5w30 will cause engine damage over 30F. Prove it. Prove the amsoil results wrong. It was proof enough that the shear force with a thin oil is just as good as a thick oil.

Per racing beat, "The oil temp never exceeds 250 degrees F without severe engine damage due to other factors".
Too many people waste too much time worrying about outdoor temperature and oil weights. Outdoor temps are overly used for choosing oil. But, thats they way we've been doing it for years.

Regardless of what weight oil is used, there are 2 oil thermostats that maintain temp. One needs to be fully open at 140F(eshaft) and the other is fully open at 150F(oil cooler) per '91 FSM.
Even in the winter, the oil temperature is kept over 100+F. So, why doesn't the 5w30(which causes damage above 30F), work so well when it is kept hot in the winter?

Icemark

Okay more backing up and lessons on oil, some of this I am sure you already know, but I will post it anyway for the benifit of others reading this thread.:

Oil companies provide data on their oils most often referred to as "typical inspection data". This is an average of the actual physical and a few common chemical properties of their oils. This information is available to the public through their distributors or by writing or calling the company directly.

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

Multi viscosity oils are one of the great improvements in oils, but they should be chosen wisely. Always use a multi grade with the narrowest span of viscosity that is appropriate for the temperatures you are going to encounter. In the winter base your decision on the lowest temperature you will encounter, in the summer, the highest temperature you expect. The polymers can shear and burn forming deposits that can cause ring sticking in piston engines and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that range. This has caused problems in diesel and two stroke engines [which some people consider our engines to be], but fewer polymers are better for all engines.

Now to back up what you were saying about viscosity:
Viscosity Index is an empirical number indicating the rate of change in viscosity of an oil within a given temperature range. Higher numbers indicate a low change, lower numbers indicate a relatively large change. The higher the number the better. This is one major property of an oil that keeps bearings and oil pumps happy. These numbers can only be compared within a viscosity range. It is not an indication of how well the oil resists thermal breakdown.

So let compare a couple typically used oils:
lets say Castrol's GTX in 20W50 and 5W50, and AMsoil 20W50 and 5W30, and Valvoline All Climate in the same 20W50 and 5W30 wieghts:

20W-50
AMSOIL 136 482 -38 <.5 ---
Castrol GTX 122 440 -15 .85 .12
Valvoline All Climate 125 430 -10 1.0 .11

And now 5W30 oils:
AMSOIL 168 480 -76 <.5 ---
Castrol GTX 156 400 -35 .80 .12
Valvoline All Climate 135 405 -40 1.0 .11

The first number is Viscosity range. Although again typically the higher the number the better. In our discussion it matters little, but intresting to note that even the 5W30 from Valvoline is within 12 points of the 20W50 a considerably thicker oil.

The second number is the Flash point. That is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil. The lower the flash point the greater tendency for the oil to suffer vaporization loss at high temperatures and to burn off on hot cylinder walls and pistons and rotors. The flash point can be an indicator of the quality of the base stock used. The higher the flash point the better. 400 F is the minimum to prevent possible high consumption in piston motors and 410-425 F in rotaries, deisels and other two strokes. Flash point is in degrees F. Too low of a number here does directly lead to oil break down on cars with lower compression.

The third number is Pour point, which is 5 degrees F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. This measurement is especially important for oils used in the winter. A borderline pumping temperature is given by some manufacturers. This is the temperature at which the oil will pump and maintain adequate oil pressure. This was not given by a lot of the manufacturers, but seems to be about 20 degrees F above the pour point. In cooler temps such as under 30F the lower the pour point the better. Pour point is in degrees F.

the forth number is % of sulfated ash and how much solid material is left when the oil burns. A high ash content will tend to form more sludge and deposits in the engine. Low ash content also seems to promote long valve life in piston engines.

and the 5th number is the % of Zinc. Zinc is used as an extreme pressure, anti- wear additive, and 11% is considered by the SAE enough to protect an automobile engine for the extended oil drain interval, under normal use. Those of us with high revving, air cooled motorcycles or turbo charged cars or bikes might want to look at the oils with the higher zinc content.

So based on that well published information with the exception of the amsoil, all the non-synthetic 5W30 oils fail the flash point test (my own opinion is that the oil cooler prevents the oil from heating sufficently in sub freezing temps and that is why it is recommended by Mazda), but work great on the pour point (which is again only important in cooler weather).

So as far as answering your comments on give you proof, I can only give you numbers, and manufacture requirements. I can't say without any doubt that the numb head that used 5W30 in his rotary motor and that is why his motor failed at 120K miles instead of 180K or 200K miles, but based on that information it should be easy to see that it is indeed likely.

Maybe some of the people that rebuild rotaries more often than me like Kevin or at Atkins or Mazdatrix can prove using too light of oil in too warm of a temp will lead to engine failure.

deadRX7Conv

I haven't seen too many rotaries die because of oil issues(unless running out of oil). Most puke an apex seal or loose the coolant seals. Most engine builders don't even bother replacing some of the engine bearings. Proof that Mazda did a good job with the oiling in the engine.

The VTR website your info came from proves nothing.

If the thin oil fails the flashpoint test, what does that mean? Nothing. The numbers weren't a test but a measurement on fresh oil out of the bottle.
The oil cooler has a thermopellet. The oil temperature in the engine never even approaches flash point. The only time flash point should be considered is during oil injection. Lower is better for the rotary. One reason why we shouldn't use synthetics.

I will not argue with Mazda's oil recommendations other than it is dated. Compare the '91 manual to the '86 manual. See attached pic. Sorry for the "paint" edit but I don't use photo software. Notice that Mazda doesn't even list thick oils in the newer book.

Its funny that gearoils with significantly higher numbers have the same viscosity as thin motor oils.
Why is the important VI spec not listed? Why is the VR spec listed if they said it wasn't important? Don't confuse the two.
http://www.vtr.org/maintain/oil-overview.html

Also notice that the oil in 1986 was SF quality and that we are now using SJ quality. The oil changed in 1989 to SG. By 1991, thick oils were left out of the oil recommendations. Anyone wanna guess why? I wonder what the requirement was in 1990.
http://www.exxon.com/exxon_productda...ategories.html

Icemark

Its hard to see in your scan but it still appears that Mazda does not recommend 5W30 used above 30F on any of your charts??? Which goes back to the guy who started this threads question. Which again tells me: it is bad to use the wrong weight at the wrong temps.

But back to your posts: Basically if I understand your argument, is that what Mazda claimed is the correct oil for the car is not correct, as technology has changed in manufacturing the oil.

But that still doesn't address the fact there were progressively more engine failures for the later models, starting with the late series 5 cars on up, with the oil requirements forced to change for emissions or what other issues that forced the dropping of some weights oils from your chart. And although you suggest that oil related failure is not common, I personally suspect that even Apex seal failure can be related to movement in the E-shaft by insufficient lubrication film, as well by insufficient flash point on the oil injected to lubricate those same seals. Again flash point is important, as you don't want the oil burning as soon as it hits the hot rotor face, you want it to burn as part of the combustion cycle.

From Exxon's site: Since our motors are relatively low speed (most people shift under 6000 RPM, well alone at 8000 RPM which is considered the start of high speed), and high pressure, (above 30 psi), and most surely high temp compared to a piston engine which uses very little of its oil for cooling purposes, I stand by my recommendation.

Icemark

Oh and as far as your posting on the SJ and other ratings, the switch in 89 to SG was for anti-sludge reqirements in Domestic built vehicles, it had no film strength changes. While SH had only purity changes (minimal foreign object particle size and foreign object reaction to temps). I actually use SL designations in my cars (which Castrol 20W50, 5W30 and 10W30 is) but of course the rotary powered car only gets the 20W50 as I never see temps under 20F.

But ideally yes if people looked at the alpha designations, then they should really be looking for CD-CF oils for severe duty with low deposit and anti-wear formations. But most oil manufactures don't post the C numbers anymore.